Production of hydrocarbon solvents of low acid wash color



Jan. 17, 1956 LOVE ET AL.

Filed Jan. 28, 1953 "EA r RECYCLE HYDROGEN 3 1, HYDROFORMING HYDROGENATION y.

2am; zguz 15 [:1 I8 I9 22 $EPARATOR HYDROJGEN 20 COOLER 23 coousn 25 RAFFINATE 32 w 5! 4/ 40 E l al c T lzN 39 64 To 2000f 2 L SULFUR ZME 010x105 ,28

PARAFF'INIC Finer/N2J WASH on. 4 2

49 ARONATIC FRACTION 3a 3 0 2s 37 Q 5. j 3/ ,27 50 T3 47 EXTYRACT z 44s. 54 1m 29 i 33 WASH OIL

F'l C3.

00F. 7 A010 5 I v V FIG. 2.

COLOR 500 o 50 INVENTOR- Roberf M. Love,

y Richard E. Tannich,

dan -1 ATTOR EY.

United States Patent PRODUCTION OF HYDROCARBON SOLVENTS 0F LOW ACID WASH COLOR Robert M. Love and Richard E. Tannich, Baytown, Tex., assignors, by mesne assignments, to Essa Research and Engineering Company, Elizabeth, N. J., a corporation of Delaware Application January 28, 1953, Serial No. 333,682

8 Claims. (Cl. 260-668) The present invention involves a process for producing hydrocarbons having a low acid wash color and involves subjecting a hydrocarbon, which may be a naphthenic hydrocarbon fraction boiling in the range between 200 and 300 F. and containing a small amount of olefins, to hydroforming conditions to form a product having a high acid wash color. The total product from the hydroforming operation is then cooled to a temperature below the hydroforming temperature and is immediately subjected to contact with a hydrogenation catalyst to form a second product without intervening storage. The product from the hydrogenation operation is then distilled to recover fractions boiling in the range between 200 and 300 F. and following the distillation operation subjected to solvent extraction in the presence of a solvent selective for removal of aromatic fractions to form an extract and rafiinate phase. The rafiinate and extract phases may then be subjected to distillation to recover fractions boiling in the range between 200 and 300 F. having solvent properties and low acid Wash colors.

This application is a continuationin-part of Serial No. 157,094, entitled Production of Hydrocarbon Solvents, filed April 20, 1950, now abandoned, in the names of Robert M. Love and Richard E. Tannich.

The invention will be further illustrated by reference to the drawing in which Fig. 1 illustrates a preferred mode of practicing the invention, and

Fig. 2 is a plot of data showing the relationship between acid wash color of one of the solvent fractions and the feed rate of the hydrogenation step at two different temperature levels. 1

Referring now to the drawing and particularly to Fig. 1, numeral 11 designates a charge line through which a feed stock such as one having the following analysis is introduced from a source not shown.

TABLE I Boiling range, F 200-300. Olefins, percent volume Less than 1.0. Aromatics, percent volume 5-15. Parafiins, percent volume 35-55. Naphthenes, percent volume 40-50.

A feed stock having the composition indicated in Table I is passed through line 11 through a heating unit or heat exchanger 12 wherein its temperature is raised to a hydro forming temperature, for example a preferred temper ature in the range between 850 and 1100 F. and then discharged by line 13 into a hydroforrning zone generally indicated as 14, which will comprise hydroforrning reactors and other auxiliary equipment as well known to the art. The average reaction temperature in the hydroforming zone is preferably in the range between 925 and 950 F. Hydrogen is introduced into hydroforming zone 14- by line 15in an amount sutficient for the reaction and usually approximately 2000 cu. ft. per barrel of feed. Hydroforming zone 14 is a catalytic hydroforming zone and a suitable hydroforming catalyst such as an oxide of 'ice chromium, molybdenum or vanadium supported on a suitable support such as alumina or zinc spinel, is provided for contact with the hydrogen and the feed mixture. The feed charged to hydroforming zone 14 by line 13 may be routed therethrough at a space velocity of 1.0 volume of feed per volume of catalyst per hour and. at the temperatures obtaining and at a preferred pressure of 215 p. s. i. g. causing the naphthenes in the feed to be converted to aromatics. The operation in hydroforming zone 14 results in the production of a product having a high concentration of aromatics, but having a relatively high concentration of components such as cyclopentadienes and the like which cause solvents produced therefrom as described below to have a high acid wash color as determined by the ASTM test method D848.47. This high acid wash color product is discharged from zone 14 by line 16 and passes through heat exchanger or cooler 17 wherein its temperature is reduced to a temperature below 700 F. which may suitably be in the range between 550" and 700 F. with a preferred temperature of 600 to 650 F.; the effluent vapor from cooler or heat exchanger 17 discharges immediately by line 18 into a hydrogenation zone 19 without intervening or intermediate storage between the hydroforming operation, the cooling step, and the hydrogenation zone. The time elapsed between hydroforming zone 14 and hydrogenation zone 19 is in the range between 0.1 and seconds and usually will be about 1 to 10 seconds. Good results may be obtained when the time between zones 14 and 19 is within the range between 1 and 60 seconds. Zone 19 is shown as a block in the flow diagram which will be understood to include a catalytic hydrogenation reactor and all auxiliary facilities therefor which are well known to the art. The total product from zone 14, including unreacted hydrogen and the unreacted feed and the reacted products, thus pass immediately and directly into hydrogenation zone 19 at a temperature such as set out before, no extraneously added hydrogen being added. Under these conditions the acid wash color forming components which may include cyclopentadienes which polymerize on storage are removed or converted to harmless compounds. It is believed that the bad actors are principally diolefins which are contained in the product from hydroforming zone 14 and which are saturated to form paraffins or mono-Olefins, resulting in a drastic lowering of the acid wash color of the solvents subsequently produced.

It is important that the product from hydroforming zone 14 be routed directly and immediately to the hydrogenation zone 19 within the time specified including the time for adjusting the temperatures to the desired point for hydrogenation. If the hydroformed product is condensed and allowed to remain in storage for an appreciable length of time the diolefins including cyclopentadiene and/or its homologues are polymerized to undesirable acid wash color producing bodies and are not atfected by subsequent hydrogenation treatment. In short, the advantages of the present invention are realized by hydrogenation of the hydroformed product immediately after the hydroforming operation. The catalyst provided in hydrogenation zone 19 may be a mixture of nickel and tungsten sulfides or other hydrogenation catalysts having equivalent or superior hydrogenating activity, such as platinum, Raney nickel, cobalt molybdate and the like. It has been found that other catalysts of lesser activity, for example, catalysts which require higher temperatures to accomplish the desired degree of hydrogenation, while working the same amount of bromine number reduction, do not allow the obtaining of a reduced acid wash color. Therefore, it is important that the catalysts employed in hydrogenation zone 19 be capable of hydrogenating at a temperature below about 700 F.

indicated by coil 27' whereby temperatures in zone: 2 6,are-

dj s e t 31 W bta nin O e h d; y n 8- y r q r ns, as d n ane i in up @12 0 E w i h m y: b d n he Pr u t n, qt r ot fir -Lit e re while a fraction largely boiling between 200 and 300 aud r sl dins, ome heavier fractions. o med i h w rea ion iswi hdr n; r m zo .5 n 2 n ntr du e her b t a c i t lla n. on 3% his r mil r 9 distitlatiq zo n, s. Pr ded w e tigsmsaa r llus ated y o l, o a ju ment of on it ns her inrfo rem alot ri usr c ns sire w ll u de s oo hat istill i n. Zones 26 n 30 sranmxidertw g he; u ua apo nd iq d ontact g e ipm nt w ll n n; he. a 1 uc a bell c n trays, R sshisri s fl lisr askin q pment w h is. ommsrsiall a a lable an a low ma e. Contact b wee vapors and liquids,

Q i i are. ad sted; n. f actio a o 9: .3 to retrieve overhead 2. fraction which may boil in'the range between 200 and 300 F. by line 32 while any heavier ras iq s Pro u n h ro m z 14 o n. ydrogenationzone 19 may be discharged from the system by line}; for further use as may be desired,

Under sorne conditions-it maybe desirable to take over headby line 3 2 a fraction of 205 -245 F. boilingrange which will comprise substantially toluene and withdraw. aseeond fraction as a side stream from distillation zone 30 by line 34; controlledby valve 35 which mayhave a 259-300 F. boiling range and comprise substantially xylenes. A stillthirdfraction may be withdrawn from distillation zone 30 including aromatic hydrocarbons having 9. and l0-carbon atoms in the molecule, by line 36 co1itrolled by valve 37.

The; fraction withdrawnfrom distillation zone 30 by line 34 mayibe treated in a similar manner to that with-.

wh ishe lea l n e stq dv za sybe ub. stantially toluene fraction or that the xylene fraction may.

qsl bstituted; er f wn pr ra l h fractions y berreceyered forsubsequent treatment and/ or purification as; be described. In any event, the .fraetjion with-. r y n, y,- in .0r1 4.as he ase ay s vdischarged into sglvent extraction zone, 33whicl1 is generally indi: catedas a bloclc inthe flow diagram, Zone.38-; will be, understood to comprise extraction facilities; well known to the art. It will be further understood that solvents having the ability to remove aromatic fractions from pre dominantly paraflinic fractions may be employed, such as liquid sultur dioxide, phenol, furfural, nitrobenzene nal- 3!!! 339!? 99 num ro s m n on h e-.- tw l ais o; be. understood; that a wash oil may be, used in sol-v vent ex-traction zone 38, especially when sulfurdioxide s hs slv n Sulfur dioxide is introduced into solvent extraction zone 38by line 39, while the wash oil is introduced thereto by line. 40. Solvent extraction zone 38, as mentioned before, will comprise the usual extraction towers and other equipment to allow formation of. extract and mt ate Phase t w l lt s nsie st d gt 0 95 8 wil sslae a ili is t re ie h n; m, bo h ati ast d a in e ha es Depending on the solvent employed inzonejgthesob vent ra 9 1s s p rate nde uitabl l ndi ionsof temperature and pressure and solvent to oilratios well known to the art to form an extract and rafiinate phase, the raflinate being discharged by line 41 and the extract being discharged by line 42 into a distillation zone 43 which, similar to distillation zones 26 and 30, is provided with heating means indicated by coil 44 whereby conditions are adjusted in zone 43 to allow recovery offthe, various fractions. Distillation zone. 43., like distillation zones 26 and 30, will also be provided with suitableinternal contacting equipment to obtain intimate contact between liquids and vapors. Conditions may be adjusted in distillation zone 43 to recover a light, intermediate and a relatively heavy aromatic fraction. If the fraction charged by line 32 to zone 38 is the fraction boilingbetween 200 and 300 F., toluene may be'recovered from zone 43 by line 45, while xylenes may be discharged therefrom by line 46 and heavier aromatic fractions, if any, recovered by line 47. The paratiinic wash, oil introduced into zone 38 by line 40 which has an initial boiling; point above 300 F., may be recovered from zone 43 by line 48 for further use-in zone 38.

The i fl na thd wn fromrzone. 318; by line 41,discharges thereby into distillation zone 49 which, similar to distillation zones 26, 30 and 43, is provided Withheating means illustrated by coil 50. Zone 49 is also provided with internal bafiiingequipment like-those. of zones. 26, 30.and '43, Distillation zone 49 may be provided. with a line 51 for recovering overhead a relatively light, parafiinic hydrocarbonrsolvent, an intermediate boiling parafifinic solvent by line 52 and a heavier paraflinic. hydrocarbon solvent by line 53. Heavier fractions, if any, may be discharged by line 54.

From the foregoing description taken with the drawing: itwill be apparent that; a simple; integrated process. is, provided'wherein solvents may be produced by hydroforming and hydrogenationin which the total product. from the hydroforming zone is routedimmediately within a time of 0.1 to seconds from the time it leaves the hydroformingzone through the hydrogenation zone, following which the product from the hydrogenation zone is subjected toa series of recovery steps to recover both; paraflinic solvents having a low bromine number and low acid wash colors and aromatic solvents having low acid wash colors and bromine numbers.

The conditions obtaining in hydroforming zone 141wi1l.

include, an average reactor temperaturein the range-between 850and 1100? F. with a preferred temperature inthe; range between 925 and 950 F. The pressures will be in the range from to 500 p. s'.v i. g. with a; preferred, pressure of 215 p. s. i. g. The amounto fhydrogen employed in, hydroforming zone 14Jwill be in the range from 500 to 5,000 cu. ft. per barrel of feed with about 2,000 cu. ft. of hydrogen per barrel of feedpre ferred. The catalysts, asmcntioned before, may be an oxide of molybdenum, chromium, vanadiumon a suitable porous: support such as alumina-or zinc-spinel;

The liquid: space velocities obtainingin hydroforming zone 14 may be in therange from 0.5 to 5 volumes offeed per volume of catalyst per hour with apreferred space velocity of l .0 v0lumeof feed per volumeof catalystper hour.

The tern; hytliofqi'llfljng is. Well known, in the liter n and s w l ac epted, nbo n pate t. dtrad literature; for example, hydroforming operations have, been described in the literature, for example, in the Oil and Gas lournal, l\darch 27, 1941, page87, andinthe Jonrnal of the Institute of Petroleum, January 194-4, pagesfi andd, and may be characterizedasthose chemical reactions which. takeplace when hydrocarbon oils, particularly, hydrocarbons boiling in the gasolinerange; e eac tha afternper ture ess f 0 F in the. pr encevo rhvdrqgenand" a ydraformina catalyst; these reactions involvea net effect oftaking-hydrogen away rom he. hydro ar on" mol cul The he ical; mac: me involved; are. complex: but areygenerally considered,

suitably be in the range between 550 and 700 F. with,

a preferred temperature in the range between 600 and 650 F. Since the hydrogen for the reaction is provided in the product from hydrogenation zone 14 by line 16 the pressures employed in hydrogenation zone 19 will be approximately the same as those obtaining in hydroforming zone 14 and the amount of hydrogen should also be approximately the same.

As mentioned before, the catalyst employed in zone 19should be a mixture of sulfides of nickel and tungsten or other hydrogenation catalyst of equivalent or greater hydrogenation activity. As examples may be mentioned Raney nickel, cobalt molybdate, platinum and the like. It has been observed that some of the usual hydrogenation catalysts of lesser activity which require higher reaction temperatures when employed in the hydrogenation stage of. the present invention, are not suitable. 1f catalysts of the latter class are employed, bromine number reduction may be effected but the acid Wash color of the solvents produced is not correspondingly reduced.

In order to illustrate the invention further, runs were made wherein a fraction boiling in the range from 100 to 300 F. was hydroformed in a commercial unit. A product was obtained, a portion of which was distilled into fractions. A portion of the total hydroformed prod uct was then hydrogenated at a liquid space velocity of volumes of feed per volume of catalyst per hour at a temperature of 630 F. in the presence of hydrogen to obtain a hydrogenated product, which, similar to the feed, was subjected to fractionation. The following table shows the bromine numbers of the fractions before and after hydrogenation and indicates the fractions containing toluene, xylenes, and heavier solvents.

TABLE II Bromine number Feed to Hydrogenated 3 Table II indicates the boiling ranges of the gasoline and solvent fractions recovered. It also shows, that the hydrogenation step of our invention permits the retention of appreciable olefins in the fractions going to motor gasoline. This is highly desirable, in view of the well known superior anti-knock qualities of olefins over the corresponding parafiins. It willbe shown below that the acid wash color of the finished solvent fractions is remarkably improved in spite of the fact that the hydrogenation is only partial, as shown above. V

A toluene concentrate was then recovered from a hydrogenated 205 -245 F. fraction by solvent extraction, and treated with 5 pounds of acid per barrel of toluene. A xylene concentrate was also recovered in asimilar manner, but was not subjected to acid treating. Heavier aromatics including C9 and C10 concentrates were recovered without solvent extraction or acid treatment.

The corresponding fractions from the feed to the hydrogenation unitwere submitted to solvent extraction to recover a toluene concentrate, and a xylene concentrate. Heavier aromatic concentrates containing the C9 and C10 aromatics were not solvent extracted. These fractions, like the hydrogenated fractions, were tested for acid wash 6 color. Another portion of the feed to the hydrogenation zone was separated into toluene, xylene and C9 and C10 aromatic fractions and these fractions were recovered similarly and the concentrates treated with 10 pounds of sulfuric acid per barrel.

The aliphatic solvents from the 200 to 300 boiling range ratfinate of the extraction steps mentioned before were also separately recovered.

The results of these runs are shown in Table III:

1 After treat with 5 lb. H2804 per bbl.

The acid wash color of the toluene before acid treating wasconsiderably higher and is estimated to be about 5 while the bromine number is estimated to be 1.

it will be noted, comparing the hydrogenated with the unhydrogenated material, that with 5 lb. H2804 per bbl. it is possible to produce a hydrogenated toluene fraction having an acid wash color in the range from 0-1, whereas the corresponding unhydrogenated fraction without acid treatment had an acid wash color of 12, while with 10 lb. H2504, the acid wash color was in the range of 6-7. It will be noted that the bromine number of the hydrogenated toluene solvent was 0.2 whereas the bromine number of the unhydrogenated stock treated with 10 lb. H2804 was 0.1, while for the unhydrogenated fraction without acid treatment the bromine number was 3.0. The xylene fraction produced in accordance with the present invention had a low acid wash color in the range between 3-4, whereas that of unhydrogenated stock treated with 10 lb. H2804 per bbl. was in the range of 4-5, and without acid treating it had an acid wash color of 10. The bromine number of the xylene fraction produced in the present invention was 0.8, sufiiciently low to meet specification.

it is to be especially noted that the C9 and C10 aromatic solvent had a Saybolt color of 30, whereas that produced without hydrogenation had a Saybolt color of only 10 and the bromine number was 0.4 with and 1.4 without hydrogenation.

The aliphatic solvents produced in accordance withthe present invention had a bromine number of 0.8, whereas the unacid treated product which had not been hydrogenated had a bromine number of 3.0. This is considered a significant quality improvement.

lnpassing, it might be mentioned that ordinarily where hydrogenation is not employed it is necessary to,use 15 pounds H2804. per bbl. to finish the toluene fraction, about 13 pounds H2804 per bbl. to finish the xylene fraction, and approximately 10 pounds H2804; per bbl. are required to finish the C9 and C10 aromatic fractions. Furthermore, the decrease in the olefin content of the paraffinic solvent produces a product of superior quality with respect to gum and peroxide formation and the like. 1

In order to test the effect of carrying out-,a process. following the operating steps ofourinvention but employing a different hydrogenation catalyst, runs were made by hydrogenating toluene and xylene fractions from a hydroformate over a hydroformingcatalyst consisting of mQlybdenasupportcdon alumina, which is known to be a: hydrogenation catalyst; at proper reaction conditions; The acid wash colors and bromine numbers of the hydrogenated and solvent extracted fractions are recorded in Tablev I,V.

The original bromine numbers of the unhydrogenated fractions were substantially those given in Tabie ii, i; e. about 4.4" for the toluene and about 2.7 for the xylene fraction. It is seen: that, in these runs, the bromine number reduction of the toluene fraction was about the same as that obtained in the. run. over nickel-tungsten sulfidehydrogenation catalystyreported.- in the first column of. Table III, and the bromine. number reduction-of the xylene fraction was considerably. greater. theless, the acid wash color" of each. fraction wasv appreciably: higher. Furthermore, it is seen that even this amount of reduction was. obtained only underv much more severe hydrogenation conditions than we. desire to. employ. incur. invention.

Data from. runs while hydrogenating a. hydrocarbon fraction at. 600? and 7.00 at liquid space-velocities varying. from about,5.to about 45.v./v./ hr. were. obtained andthc acid. washcolor of. the. xylene concentrate determined. Theseruns arepresented' graphically in. Figure IL which showsthatat. 600 F. the. curve for the. acid wash. color plotted. against the space velocity reaches a maximumacid wash color. at about 45 v./v./hr. and that an acid. wash color of. about. 5, is. obtained at about.1.5 v./v./hr On the other hand', at' 700 F. the. acid wash color beginsinitially at, about 5 and rapidly increases to.-7 atabout 30. In short, thedata in Figure 11 shows thatit will be desirable to operate ata temperatureinthe range between 600 'and'6'50 Fl at .spacevelocities from about 8 to 45fv./v./hr. with a preferred'space velocity of approximately 10.

In order to show the advantages of the present invention over anoperation where the product from ahydroforming zone was stored prior to hydrogenation a run was made. in which .a product was obtainedfrom a commerciali'hydroforming unit which. was. charging a 200 to 300 F. naphtheni'c. hydrocarbon fraction over conventional molybdena-on-alumina hydroforming catalyst under conventional" hydroforming' conditions of." about 930 average catalyst bed temperature; 250p. s; i. g. pressure, liquid' spacevelocityof-1v;/v./hr;, and'a recycle gas rateof" 2000 standard cubic feet per barrel of feed; A portion of the liquid fraction of this hydroformed product; boiling between approximately 100"and 350 F., was condensed and stored at atmospheric temperature under a nitrogen blanket for a period in excess oi -two weeks.- This ,fraction was thenhydrogenated over anickel-tungsten. sulfide catalyst; which. had been on genateth product was" condensed andii-fractionatetfi. and? the 'acidiwasli color of the" fraction boiling between 200 and 2 50 FL was determined and"found 'to be 4 and that of thetfraction boiling-between -25 0- and 300 Fl was found Never to be intermediate between 5 and 6; The xylenes portion of--theproductwas segregated and extracted with liquid S02 to, eliminate non-aromaticstherefrom and the acid wash color of'the extracted xylenes was subsequently determined and found, to be 5; The bromine'number-ofthe feed to the hydrogenation step was 5.8, and that of the total hydrogenation product was 2.5. V

In order-to illustrate the practice of the present invention a hydrogenation unit was connected into a-hydroforming unit in which provision was made to cool the total product of the hydroforming operation without condensation and the total product was-routed into a hydrogenation unit. The product from the hyd'roforming unit was obtained while charging to the hydroforming unit a 200" to 300 F; naphthenic hydrocarbon fraction over; conventional molybdena-on-alumina hydroforming catalyst underconditions of about 930 F average catalyst period temperature. 250 lbs. p. s. i. g. liquid space velocity of 1/v.-/v.'

per hour anda recycle gas rate of about 2000 standard" cubic feet per barrelof feed. The product from the hy* droforming operation wasv obtained in vapor form at the temperature ofthe hydroformer reactor outlet, including all unconverted feed components, converted'fractions; and

gasesincluding hydrogen. The temperature of thistotal product was adjusted without intermediate condensation, and the total product without intermediate or intervening storage was. thenpassed directly over nickel-tungsten sultide catalyst which had been on stream for l23days, at a tempcrature.of'623 F., a pressure of 190 lbs. p. s. i. g.,.

totalproduct from the hydroforming operation contacted. the hydroforming catalyst nearly immediately.

termined. andfound to be 4. The bromine numberjof the.

feedto the-hydrogenation step. was 4.6, and .that'of. the total hydrogenated product was 2.4.

Comparing the data of the runwhere. the product from.

the hydroforming operation was stored' and the product from the run where there was no intervening storage and I the product was passed immediately into the hydrogenation zone it will be seen that substantially better acidvwash color; particularly in the 200"to 250 F. fraction was ob? tained: and that this: improvement 'was obtained spite of the factv that the hydrogenation catalyst in' the run where the-practice of the present'invention was employed was of greater age than in the run where intervening storageof the product obtained. It is believed..that;the practice-of the present invention resultsin substantially improved acid washcolor because of the: fact that. cyclo-. pentadiene and/or'its'homologues. are: present in; 11115311).- droformedproduct. It" is believedithatthe.cyclopentadiene polymerizes' on condensation and' stora'gewhich results inthe formation of compounds which contribute to. poor acid wash color.

The'practice of the. present invention, which .resultsin reduction-of acid wash colorqof. the-*hydrofonned and hydrogenated product, allowstheobtaining'of substantial. monetary savingssince otherwise it wouldbe' necessary to treat"theliydroformed'productwith large amountsoiialcid: tel-obtain the-:d'esired acid wash" colorwhich: the present invention allows: Acid treatment" of: thcahydroformed product results'in loss of valuable -aromatic compounds Which-is obviated-in the. practice ofi the:presentiinventionz It is believed also that practice of the present invention reduces the concentration of unsaturated compounds which tend to form peroxides upon atmospheric oxidation. Such oxidation products, as exemplified by peroxides, are deleterious in subsequent processing steps such as, for example, solvent extraction with liquid S02.

The Acid Wash Color test referred to herein, namely ASTM test method D-848-47, may be briefly described as a method of testing industrial aromatic hydrocarbons of relatively high purity by agitating three volumes of the aromatic with one volume of concentrated (96i0.5%) sulfuric acid for 20 seconds, permitting the layers to separate, and comparing the color of the acid with a set of standards, which are numbered from (water white) to 14 (the color of half saturated aqueous KzCrO-r). The test is an indication of the presence of undesired highly reactive compounds, such as diolefinic materials, which have a tendency to interfere in reactions and processes in which the aromatics may be employed.

The bromine numbers referred to herein were determined by a modified Lewis and Bradstreet method. The numbers are numerically equal to centigrams of bromine consumed per gram of sample.

While the present invention has been described with respect to specific examples, it will be understood that the process may be varied without departing from the spirit and scope of the invention. For example, while the process is particularly applicable to the production of aromatic solvents, it is also applicable to the production of parafiinic solvents and it is specifically contemplated that it may be used for the production of both types of solvents.

The nature and objects of the present invention having been completely described and illustrated, what we desire to claim as new and useful is:

1. A method for producing hydrocarbon solvents having a low acid wash color which comprises the steps of hydroforming a naphthenic hydrocarbon fraction containing a small amount of olefins less than about 2% by volume and boiling in the range between 200 and 300 F. under hydroforming conditions of temperature and pressure in a first zone to convert naphthenes to aromatics and to form a total first vaporous product including unreacted hydrogen, unreacted feed and reacted products having a high concentration of acid wash color forming bodies in the 200 to 300 F. boiling range, reducing the temperature of the total first product to a temperature below 700 F., immediately passing said total vaporous first product at said reduced temperature after said total first product leaves said first zone into a second zone, hydrogenating said total first product in said second zone in the absence of extraneously added hydrogen in the presence of a hydrogenating catalyst selected from the group consisting of nickeltungsten sulfide, platinum, Raney nickel, and cobalt molybdate at a temperature below 700 F. and at a space velocity higher than a space velocity in said hydroforming step to form a second product having a low concentration of acid wash color forming bodies in the 200 to 300 F. boiling range and distilling said second product to recover a fraction boiling in the range between 200 and 300 F. having solvent properties and an acid wash color not in excess of 6.

2. A method in accordance with claim 1 in which the low acid wash color product is an aromatic hydrocarbon fraction.

3. A method in accordance with claim 1 in which the low acid wash color product is a parafiinic hydrocarbon fraction.

4. A method in accordance with claim 1 in which the low acid wash color product is recovered by distillation followed by solvent extraction at low temperatures with liquefied sulfur dioxide in the presence of a paraffinic wash oil having a boiling point above 300 F.

5. A method for producing hydrocarbon solvents have ing a low acid wash color which comprises the steps of hydroforming a naphthenic hydrocarbon fraction containing a small amount of olefins less than about 2% by volume and boiling in the range between 200 and 300 F. under hydroforming conditions of temperature and pressure in a first zone to convert naphthenes to aromatics and to form a total first vaporous product including unreacted hydrogen, unreacted feed and reacted products having a high concentration of acid wash color forming bodies in the 200 to 300 F. boiling range, reducing the temperature of the total first product to a temperature in the range between 500 F. and 700 F., immediately passing said" total vaporous first product at said reduced temperature within a time in the range between 0.1 and seconds after said total first product leaves said first zone into a second zone, hydrogenating said total first product in said second zone in the absence of extraneously added hydrogen in the presence of a hydrogenating catalyst selected from the group consisting of nickel-tungsten sulfide, platinum, Raney nickel, and cobalt molybdate at a temperature in the range between 550 F. and 700 F. and at a space velocity higher than a space velocity in said hydro forming step to form a second product having a low concentration of acid wash color forming bodies in the 200 to 300 F. boiling range and distilling said second product to recover a fraction boiling in the range between 200 and 300 F. having solvent properties and an acid wash color not in excess of 6.

6. A method in accordance with claim 5 in which the hydrogenation temperature is in the range between 600 and 650 F. and the hydrogenation liquid space velocity is in the range between 8 and 45 volumes of feed per volume of catalyst per hour.

7. A method for producing hydrocarbon solvents having a low acid wash color which comprises the steps of hydroiorming a naphthenic hydrocarbon fraction containing a small amount of olefins less than about 2% by volume and boiling in the range between 200 and 300 F. under hydroforrning conditions of temperature and pressure in a first zone to convert naphthenes to aromatics and to form a total first vaporous product including unreacted hydrogen, unreacted feed and reacted products having a high concentration of acid wash color forming bodies in the 200 to 300 F. boiling range, reducing the temperature of the total first product to a temperature in the range between 500 F. and 700 F., immediately passing said total vaporous first product at said reduced temperature within a time in the range between 1 second and 60 seconds after said total first product leaves said first zone into a second zone, hydrogenating said total first product in said second zone in the absence of extraneously added hydrogen in the presence of a nickel-tungsten sulfide catalyst at-a temperature in the range between 550 F. and 700 F. and at a space velocity higher than a space velocity in said hydrotorming step to form a second product having a low concentration of acid wash color forming bodies in the 200 to 300 F. boiling range and distilling said second product to recover a fraction boiling in the range between 200 and 300 F. having solvent properties and an acid wash color not in excess of 6.

8. A method for producing hydrocarbon solvents having a low acid wash color which comprises the steps of hydroforming a naphthenic hydrocarbon fraction containing less than about 2% by volume of olefins and boiling in the range between 200 and 300 F. at a temperature in the range between 850 and 1100 F. at a pressure in the range between and 500 p. s. i. g. and at a space velocity in the range between 0.5 and 5.0 volumes of feed per volume of catalyst per hour in a first zone to convert naphthenes to aromatics and to form a total first product including unreacted hydrogen, unreacted feed and reacted products 'having a high concentration of acid wash colorforrning'bodiesin the 200 to 300" F} boiling said total first product'in said second zone in the absenceof" ext'raneously added" hydrogen in the presence of a nickel-tungsten sulfide: catalyst at a temperature-in the range from 600 to 650 F. and-at a space velocity in therange between 8 and 45 volumes of feed per volume of catalyst per hour toforrn a" second product having a lowconcentration of acid wash color formingbodies in the 200? to 300 F. boiling range, distillingsaid second product to recover a fraction boiling in the same range as saidnaphthenic hydrocarbonfraction, extracting said' recoveredfrac'tion with a solvent selective for removal.

of aromatic fractions to'forman extract and'a' raffinate phase, and separately recovering fromsaid phases frac tions having acid wash. colors not in excess of 6 and solvent properties.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Brandt ct 211., Industrial and Eng. Chenn, vol. 39'; No. 8 (August 1947), pages 1010-4018 (9 pages 

1. A METHOD FOR PRODUCING HYDROCARBON SOLVENTS HAVING A LOW ACID WASH COLOR WHICH COMPRISES THE STEPS OF HYDROFORMING A NAPTHENIC HYDROCARBON FRACTION CONTAINING A SMALL AMOUNT OF OLEFINS LESS THAN ABOUT 2% BY VOLUMBE AND BOILING IN THE RANGE BETWEEN 200* AND 300* F. UNDER HYDROFORMING CONDITIONS OF TEMPERATURE AND PRESSURE IN A FIRST ZONE TO CONVERT NAPHTHENES TO AROMATIC AND A FORM A TOATL FIRST VAPORS PRODUCT INCLUDING UNREACTED HYDROGEN, UNREACTED FEED AND REACTED PRODUCTS HAVING A HIGH CONCENTRACTION OF ACID WASH COLOR FORMING BODIES IN THE 200* TO 300* F. BOILING RANGE, REDUCING THE TEMPERATURE OF THE TOTAL FIRST PRODUCT TO A TEMPERATURE BELOW 700* F., IMMEDIATELY PASSING SAID TOTAL VAPOROUS FIRST PRODUCT AT SAID REDUCED TEMPERATURE AFTER SAID TOTAL FIRST PRODUCT LEAVES SAID FIRST ZONE INTO A SECOND ZONE, HYDROGENATING SAID TOTAL FIRST PRODUCT IN SAID SECOND ZONE IN THE ABSENCE OF EXTRANEOUSLY ADDED HYDROGEN IN THE PRESENCE OF A HYDROGENATING CATALYST SELECTED FROM THE GROUP CONSISTING OF NICKELTUNGSTEN SULFIED, PATAINUM, RANEY NICKEL, AND COBALT MOLYBDATE AT A TEMPERATURE BELOW 700* F. AND AT A SPACE VELOCITY HIGHER THAN A SPACE VELOCITY IN SAID HYDROFORMING STEP TO FORM A SECOND PRODUCT HAVING A LOW CONCENTRATION OF ACID WASH COLOR FORMING BODIES IN THE 200* TO 300*F. BOILING RANGE AND DISTILLING SAID SECOND PRODUCT TO RECOVER A FRACTION BOILING IN THE RANGE BETWEEN 200* AND 300* F. HAVING SOLVENT PROPERTIES AND AN ACID WASH COLOR NOT IN EXCESS OF
 6. 